Read the rules about fire on pages 18 and 19 of the rulebook.
The Event Cards “Descent” and “Fast Descent” add to the Pressure Track, while “Reactor Warmup” and “Reactor Malfunction”
add to the Heat Track.
Fires are a little more complicated. A fire adds to the Asphyxiation Track if the room where the fire starts is not already flooded. See “Fire Events,” below.
When a fire starts, the fire’s location must be determined. Most of the time, the location is decided randomly, by die roll. If the room selected is already flooded, no new fire starts.
If a non-flooded room is selected, the Asphyxiation Track increases by one, even if the selected room already has a Fire token in it.